SCHEMA.md

SCHEMA — Scandium-Dataset v1.0.0

File: entries_v4_typed.parquet

Rows: 267,230
Columns: 47
Storage: Typed Parquet (PyArrow) with proper int/float/bool types
Index: entries_v4_typed.index.json — O(1) lookup by source_id

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Column Dictionary

#	Column	Type	Unit	Nullable	Description	Source Field Mapping
1	source	string	—	No	Source database: "mp", "oqmd", "jarvis", or "experimental"	All
2	source_id	string	—	No	Original ID in the source database (e.g. mp-12345, oqmd-67890, JVASP-123)	MP: material_id; OQMD: id; JARVIS: jid
3	formula	string	—	No	Pretty chemical formula (e.g. Li6PS5Cl)	All
4	structured_formula	string	—	No	Reduced/structured formula via pymatgen reduced_formula	Computed
5	band_gap	double	eV	Yes (151 OQMD entries)	Electronic band gap. null when calculation did not converge.	MP: band_gap; OQMD: band_gap; JARVIS: bandgap
6	formation_energy_per_atom	double	eV/atom	No	Formation energy per atom. Negative = stable relative to elements.	MP: formation_energy_per_atom; OQMD: delta_e; JARVIS: formation_energy
7	energy_above_hull	double	eV/atom	Yes (8,933 JARVIS + 5,238 others)	Energy above convex hull. null when chemical system has <3 entries (hull construction impossible) or JARVIS subset lacks hull coverage.	MP: energy_above_hull; OQMD: delta_e_hull; JARVIS: computed via internal hull
8	nsites	int64	atoms	No	Number of atoms in the conventional unit cell	All (from structure)
9	nelements	string	—	No	JSON array of element symbols (e.g. ["Li","P","S","Cl"])	Computed
10	volume	double	ų	No	Unit cell volume	MP: volume; OQMD/JARVIS: computed from lattice vectors
11	density	double	g/cm³	No	Computed density from atomic masses and volume	Computed
12	mobile_ion	string	—	No	Mobile ion carrier: "Li", "Na", "Mg", or "None"	Computed (composition heuristic)
13	tier	string	—	No	Quality tier: "gold", "validated", "raw", "experimental_gold"	Computed (11-gate system)
14	quality_score	int64	score (0–88)	No	Composite quality score from 5 sub-scores. Range 48–88 (conservative; no entry ≥90)	Computed
15	is_experimental	bool	—	No	true if entry is from experimental data (OBELiX), false otherwise	Computed
16	is_stable	string	—	No	Stability flag: "True", "False", or "null" (lacking hull data)	MP: is_stable; OQMD: is_stable; JARVIS: computed
17	is_metal	bool	—	No	true if band gap ≤ 0.1 eV	Computed from band_gap
18	space_group	int64	number	Yes (16 OQMD entries)	International space group number (1–230). null when spglib fails (disordered or too few atoms).	Computed via spglib
19	space_group_number	string	—	Yes	Space group number as string (for compatibility)	Computed
20	crystal_system	string	—	Yes	Crystal system: "triclinic", "monoclinic", etc.	Computed
21	sse_family	string	—	No	SSE structural family classification: "garnet", "NASICON", "argyrodite", "LGPS_type", "LISICON", "anti_perovskite", "perovskite", "halide", "borohydride", "sulfide", "oxide", "none"	Computed (composition-based heuristic)
22	license	string	—	No	Entry-level license: "CC-BY-4.0", "CC0-1.0", or "OQMD-noncommercial"	Per-source
23	duplicate_group	int64	—	Yes (245,490 are null)	Group ID for entries with identical formula from multiple sources. Non-null only for members of duplicate groups.	Computed
24	source_weight	double	—	No	Relative source weight for ensemble modeling (0.0–1.0). Reflects source-level confidence.	Computed
25	total_magnetization	double	μB	Yes (non-magnetic entries)	Total magnetic moment. 0.0 for non-magnetic systems; null if unavailable.	MP: total_magnetization; OQMD: total_magnetization; JARVIS: magmom
26	fe_per_carrier	string	eV/carrier	Yes	Formation energy per mobile ion carrier for battery-relevant entries.	Computed
27	volume_per_carrier	string	ų/carrier	Yes	Volume per mobile ion carrier.	Computed
28	carrier_fraction	double	—	Yes	Fraction of sites occupied by mobile ions	Computed
29	electronic_insulation	bool	—	No	true if band gap ≥ 1.0 eV (rough electronic insulation criterion)	Computed
30	space_group_symbol	string	—	Yes	Hermann-Mauguin space group symbol (e.g. "P-1", "Fm-3m")	Computed via spglib
31	magnetic_ordering	string	—	Yes	Magnetic ordering classification: "NM" (non-magnetic), "FM" (ferromagnetic), "AFM" (antiferromagnetic), "FiM" (ferrimagnetic), or null	Computed
32	structure_json	string	—	No	JSON-serialized pymatgen Structure object. Contains lattice parameters, site positions, species.	All sources
33	ssb_screening	string	—	No	JSON block of SSE screening fields (see SSB Screening sub-schema below).	Computed
34	provenance	string	—	No	JSON block of provenance tracking fields (see Provenance sub-schema below).	Computed
35	elements	string	—	No	JSON array of all elements present (space-separated for some sources)	All sources
36	families	string	—	No	JSON array of battery-relevant family classifications	Computed
37	carrier_elements	string	—	Yes	JSON array of mobile carrier elements (Li, Na, Mg) if present	Computed
38	quality_flags	string	—	Yes	JSON array of quality defect flags (empty if none)	Computed
39	tags	string	—	Yes	JSON array of user-facing tags (e.g. ["single_atom"], ["extreme_fe"])	Computed
40	notes	string	—	Yes	Free-text notes about the entry	Computed
41	anions	string	—	Yes	JSON array of anion elements present	Computed
42	strict_gold	string	—	No	Strict Gold eligibility: "True" or "False"	Computed
43	tier_detail	string	—	No	JSON dictionary of tier classification details	Computed
44	tier_gates	string	—	No	JSON dictionary of gate pass/fail flags (G0–G11)	Computed
45	quality_sub_scores	string	—	No	JSON dictionary of 5 quality sub-scores: geometry, dft, metadata, novelty, chemical	Computed
46	references	string	—	Yes	JSON array of literature references for the entry	All sources
47	merged_sources	string	—	Yes	JSON array of source IDs merged into this entry during deduplication	Computed

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Sub-schemas

provenance (JSON block)

{
  "source": "mp",
  "source_id": "mp-12345",
  "download_date": "2026-07-20",
  "processed_at": "2026-07-21T18:30:00Z",
  "version": "v1.0.0",
  "repairs_applied": ["repair_coordinate_artifact", "repair_volume"],
  "checksum": "sha256:abc123..."
}

Field	Type	Description
source	string	Source database name
source_id	string	Original ID in source
download_date	string	Date when raw data was extracted from source API (ISO 8601)
processed_at	string	When the entry was processed through the pipeline (ISO 8601)
version	string	Dataset version that created this entry
repairs_applied	array of strings	List of all repairs applied to this entry (empty if none)
checksum	string	SHA-256 checksum of the entry's structure + properties JSON blob

ssb_screening (JSON block)

{
  "sse_candidate_score": 12,
  "gates_passed": ["thermo_stability", "electronic_insulation"],
  "thermo_stability_flag": true,
  "stability_window_low_V": 0.0,
  "stability_window_high_V": 5.2,
  "window_width_V": 5.2,
  "interfacial_reaction_energy_vs_Li_eV_atom": 0.15,
  "passivating_interphase": true,
  "bulk_modulus_GPa": 35.2,
  "shear_modulus_GPa": 18.1,
  "dendrite_suppression_flag": true,
  "bvse_migration_barrier_eV": 0.42,
  "has_bvse_barrier": true,
  "bvse_skip_reason": null,
  "cavd_channel_dimensionality": null
}

Field	Type	Coverate	Description
sse_candidate_score	int	100%	5-gate composite score (10 base + 1 per gate passed). Range 10–15.
gates_passed	array	100%	List of passed gate names
thermo_stability_flag	bool	99.8%	True if E_hull < 0.025 eV/atom
stability_window_low_V	float	0.7%	Lower bound of electrochemical stability window vs Li/Li+
stability_window_high_V	float	0.7%	Upper bound of electrochemical stability window
window_width_V	float	0.7%	Width of stability window
interfacial_reaction_energy_vs_Li_eV_atom	float	14.9%	Decomposition energy vs Li metal
passivating_interphase	bool	14.9%	True if reaction products are electronically insulating
bulk_modulus_GPa	float	100%	Geometric density-based proxy (not DFT elastic tensor)
shear_modulus_GPa	float	100%	Geometric density-based proxy (not DFT elastic tensor)
dendrite_suppression_flag	bool	100%	True if shear_modulus > 6 GPa
bvse_migration_barrier_eV	float	23% Li/Na	BVSE migration barrier estimate via bvlain v0.25.1
has_bvse_barrier	bool	100%	True if BVSE barrier was successfully computed
bvse_skip_reason	string	77% Li/Na	Reason BVSE was skipped (e.g. "no BV params for composition", "max_sites_exceeded")
cavd_channel_dimensionality	string	0%	CAVD channel dimensionality (0D/1D/2D/3D). Not yet computed — see CHANGELOG.

---

Null Semantics

Null Pattern	Meaning	Examples
null in band_gap	Calculation did not converge	151 OQMD entries
null in energy_above_hull	Chemical system has <3 entries (sparse) or source does not compute hull distance	8,933 JARVIS entries
null in space_group	spglib failed (disordered, too few atoms)	16 OQMD entries
null in duplicate_group	Entry has no duplicates across sources	245,490 entries
null in total_magnetization	Non-magnetic system or field not computed	Varies
null in ssb_screening.*	Screening field not computed for this entry	CAVD (0%), stability windows (99.3%)

Never null: source, source_id, formula, structured_formula, formation_energy_per_atom, nsites, nelements, volume, density, mobile_ion, tier, quality_score, is_experimental, is_metal, sse_family, license, source_weight, electronic_insulation, structure_json, ssb_screening, provenance, elements, families, strict_gold, tier_detail, tier_gates, quality_sub_scores.

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Units Reference

Property	Unit	Notes
Formation energy	eV/atom	Per-atom, not per-formula-unit
Energy above hull	eV/atom	Per-atom
Band gap	eV	Electronic band gap (GGA-level)
Volume	ų	Conventional cell
Density	g/cm³	Computed from elements + volume
Total magnetization	μB	Bohr magnetons
BVSE migration barrier	eV	SoftBV percolation method
Stability window	V vs Li/Li+	Grand potential phase diagram
Interfacial reaction energy	eV/atom	Decomposition energy vs Li
Bulk/shear modulus	GPa	Geometric proxy (not DFT)

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Source DFT Parameter Heterogeneity

Parameter	MP	OQMD	JARVIS-DFT
Functional	PBE (Perdew-Burke-Ernzerhof)	PBE	PBE (OPT variants for some)
U correction	Hubbard U for transition metals	Custom U values (differs from MP)	No U correction (default PBE)
Pseudopotentials	PAW (VASP-supplied)	PAW (VASP-supplied, older set)	USPP / PAW (mixed)
Encodings	ENCUT = 520 eV (default +30% for some)	ENCUT = 520 eV (standard)	ENCUT varies (USPP-compatible)
k-point density	KSPACING ~0.22 Å⁻¹	Variable (denser for small cells)	Variable
Band gap method	PBE (indirect)	PBE	PBE + OPT / TB-mBJ (for some)

Important: Direct comparison of formation_energy_per_atom, energy_above_hull, or band_gap across sources is scientifically questionable due to differing DFT parameters. Cross-source agreement statistics are published in dataset/statistics/cross_source_agreement.json. See docs/limitations.md for guidance on source-aware analysis.

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Version History

Version	File	Notes
v1.0.0	entries_v4_typed.parquet	Current. Typed Parquet with proper int/float/bool columns. 47 columns.
v0.3.0	entries_v3.parquet	Previous. Un-typed Parquet, same 47 columns.
v0.0.0	entries_final_v3.json	Original JSON store (1.6 GB). Deprecated.

Migration v3 → v4: Column names and semantics are identical. v4 adds explicit PyArrow schema typing (int64, float64, bool) to enable HF Dataset viewer compatibility and streaming. No data values changed.